A system of driverless vehicles driven by frictional contact between a drive tube and a drive wheel on the vehicle is disclosed in U.S. Pat. No. 3,356,040. A vehicle of the type adapted for use herein is taught by U.S. Pat. No. 3,818,837.
A vehicle speed control transition module is described in U.S. Pat. No. 4,428,298 for automaticaly reducing or increasing the speed of a driverless vehicle as it moves along the tracks of a conveyor. The invention described in the patent includes a cam means provided along the second drive tube for slowing down or stopping a vehicle as the vehicle moves along the second drive tube. In addition, a clutch means is provided for sequentially enabling only the first motor to drive the first and second drive tubes and then only the second motor to drive the second and third tubes. The second drive tube is initially coupled to the first drive tube, is then disconnected from both the first and third drive tubes until the vehicle is slowed sufficiently, and is then coupled to the third drive tube. After the speed transition is accomplished, the second drive tube is disconnected from the third drive tube and recoupled to the first drive tube.